(There once was a Kingdom Hearts story or two where Xemnas survives and then begins recruiting new members from various anime worlds. Obviously, this one will take a page out of that book.)
Xemnas looked down on the world. Honnouji Academy, a world born from the heart of an ambitious figure. After a few discrete observations, he had wondered if this figure, Satsuki Kiryuin, was a Princess of Light. He shook the idea out of his head; even if the notion was not ridiculous, he could easily capture the other seven princesses with ease.
Xemnas noted how the school was split by population, but he was more interested in these Goku Uniforms. These uniforms gave their wearers powers, and more power was given when more Life Fibers were weaved into them. Were they stronger than Keyblade armors or Sora's Drives, or even the powers of nothingness? Perhaps not with the current selection, but he was certain there was something off about these "Life Fibers".
Over the last few months, however, things had gotten interesting. It all began when the one known as Ryuko Matoi entered Honnouji Academy. He watched as Ryuko had challenged the structure of Satsuki's world, and in turn, he saw how Satsuki struck back. These evolved Goku Uniforms they wore, the Kamui, were surely strong, but with that price of power came a sentience that would surely go against his plans. Speaking of which, he was amused that Satsuki allowed this Fight Club to form and disband if only to weed out the weak.
Xemnas could only see two potential recruits here. Satsuki Kiryuin had a strong heart, able to lead her students regardless of their ranks and never forced back into a corner. Ryuko Matoi, though, was very stubborn, yet she was adaptive and knew when to continue living. The latter was weak, but she reminded him of Sora.
Finally, the time came. Satsuki had announced the Naturals Election, an event that ensured anarchy over the coveted Three Star ranks shared by her Elite Four. Ryuko managed to get the fifth spot, and this had prompted the Elite Four to make a deal with Satsuki to fight Ryuko one-on-one.
Xemnas observed the Ryuko girl. She had fought against an opponent with a powerful defense, then later fought someone who had the advantage in the sky. Ryuko had not bothered to take a break between the fights, and had prompted two transformations and some new techniques. Ryuko was becoming more and more impressive, but Xemnas knew that Ryuko still had a long way to go if she were to challenge Satsuki.
At last, Ryuko was to face that one guy. Xemnas did not remember the man's name, only remembering that the man had purposely blinded himself to get back into Satsuki's grace. "Hey, old man, hope you don't mind if I drop in!"
Xemnas showed no fear as a sugary girl in pink had appeared next to him and then floated down to the arena. There was something...alien about that girl, but then he mentally thanked the girl as he saw a reaction from Satsuki. Satsuki has a strong heart, but she steeled it strongly against her supposed ally. She would never turn. On the other hand, that girl had pulled out a purple blade, and it drove Ryuko into a blind rage.
Xemnas smiled as Ryuko's heart filled with darkness. So, a girl who seeks the murderer of her father, only to meet the murderer who never broke that smile. Ryuko had fought until the Kamui she entrusted her life consumed her, and she was turned into a monstrosity. If this monster became a heartless, he would have to place it on the level of a Kurt Kisa.
He quickly teleported to the ground and whisked Ryuko's friends, depositing her at the edge of the school. By the time he returned, Satsuki had began fighting the monster Ryuko. Without a foolish person to interfere, Satsuki came in for the final blow, managing to thrust her blade through Ryuko's chest. Xemnas heard a gun go off, and Ryuko's body had been frozen as Satsuki managed to jump away in time. When Satsuki saw Ryuko's heart perched on her blade, her blade shook. However, this was all Xemnas needed to see to know that everything went as planned.
A girl sat on a lone beach under a nightly sky. Xemnas approached her. "How do you feel?"
"Nothing." The girl replied. "I remember...two girls, and a uniform. What are they to me?"
"They are somebody, but you cannot approach them, because you are Nobody, a being without heart." Xemnas looked to the moon over the waters. "They could be your friends, enemies, or strangers you've never met. Without a heart, you will never tell what they are, and they may as well use you."
The girl turned to him. "How do I gain a heart? Do I just grab one?"
"I'm afraid, in your case, that your original heart was destroyed." Xenmas truthfully told her. "However, I plan to create the heart of all hearts, Kingdom Hearts. It is so powerful that it would create new hearts for us. I am creating the Organization with the goal to create Kingdom Hearts, and if you join, not only will you regain your heart, but your purpose as well."
"My purpose?" The girl thought. "That's right. I fight...but for what? I suppose I fight for you, for now."
A red blade materilized in her hands. Xemnas couldn't help but smile. "Welcome to Organization XIII, Kyurox, the Bloodied Seamstress."